Not applicable.
1. Field of Invention
This invention relates to a lock nut, specifically to a nut that can be locked onto a bolt such that it cannot be removed without a key or other means to unlock it.
2. Description of Prior Art
There are many circumstances in which it is desirable to lock a nut in place once it has been positioned on a lug, or bolt, such that the nut cannot be removed without a key or other means to unlock it. Most commonly such nuts have been developed to lock wheels on cars so that the wheels cannot be stolen. Lock nuts to prevent wheel theft have typically been of three types:
One type relies on a cylindrical nut body of hardened metal with a recessed channel of irregular shape at the end opposite that of a threaded cavity. This type makes use of a special wrench as the means to unlock the nut. The special wrench is designed to fit in the irregularly shaped channel in order to grip and turn the nut. Since the outside of the nut is round in shape and hardened, common tools cannot grip it. The cylindrical shape of the nut provides no flat surface for a standard wrench to engage, and the teeth of pliers or the like typically cannot get a bite on the rounded hardened surface.
Another type is constructed to have a removable cap such that when the cap is placed and locked onto the nut, the cap rotates and prevents the removal of the nut. The cap must be removed in order to grip and turn the nut.
Still another type provides an integral rotatable cap or sleeve on the nut that includes a locking means for locking the cap or sleeve directly to the nut so that rotation of the cap rotates the nut for removal thereof. More recent designs of this type have included improvements to prevent the device from being rendered ineffective if a hammer or the like were to be used in an attempt to jam or break the locking mechanism. Other design improvements have included magnetically actuated locking mechanisms. Magnetic lock actuation eliminates the key hole that is present in a standard mechanically actuated lock. The lack of a key hole prevents the ability to pick the lock with hair pins or the like.
Exemplary of the prior art for lock nuts to secure wheels are the following U.S. Pat. Nos. 1,625,901 issued Apr. 26, 1927 to Lay, 1,937,848, issued Dec. 5, 1933 to Shinn, 2,225,132 issued Dec. 17, 1940 to Seaman, 3,540,245 issued Nov. 17, 1970 to Pope, 3,978,698 issued Sep. 7, 1976 to Ono, and 4,336,698 issued Jun. 29, 1982 to Hurd.
Another application for the use of a lock nut can be found in many heavy industry manufacturing facilities. Such nuts are often used to limit access to portions of a manufacturing process that are considered unsafe when the process is running. Examples include man-holes providing access to vessels that operate under high pressure and/or temperature, as well as cover plates providing access to machinery operating under very high speeds, such as turbines in a power plant. In order to prevent the removal of these man-holes or cover plates when conditions are not safe, it is common practice to drill a hole through the end of the bolt. Once a nut is threaded over the bolt, beyond this hole, a padlock is inserted through the hole in the bolt, thereby locking the nut in place on the bolt.
Over the years, as lock nut design changes have been made in order to better thwart any unauthorized effort to remove the nut, these changes have typically come at the expense of greater complexity of the design and hence, higher cost to manufacture. The earlier designs, comprising a single cylindrical piece with a special shaped channel, were relatively inexpensive to make but ultimately could be gripped and rotated under sufficient force by a device such as a vice grip. Later designs, with rotating caps, were less easily removed but more complex and, consequently, more expensive to manufacture. These devices could be rendered ineffective by crushing the cap against the nut such that the nut would turn when the cap turned. Still later designs, such as U.S. Pat. No. 4,336,698, while making it more difficult to crush the cap against the nut, did so at the expense of further complexity and cost to manufacture. Other simpler yet effective means to lock a nut in place, such as the method applied in many manufacturing facilities, require that a modification be made to the bolt or lug to which the nut would be attached.
The essence of the present invention is a lock nut that, in one configuration can be threaded onto a bolt and, after threading, can be transformed into a different configuration that can be locked into place, the transformed configuration being of such size and shape that the nut cannot be removed without encountering an obstruction. The application of this invention is specific to situations in which the receiving bolt is fixed in place relative to an xe2x80x9cobstructionxe2x80x9d object, and the receiving bolt cannot be rotated.
The prior art examples are advantageous in that, in each case, the means for locking the nut is entirely within the lock nut device itself. Said another way, if the nut can be threaded onto a bolt, it can be locked onto the bolt. The present invention cannot make such a claim. The present invention relies on the geometry surrounding the bolt in the specific application for which the lock nut is desired. It makes use of that geometry, specifically it relies on some object within that geometry to provide an obstruction that prevents the nut from being removed. Though its application is more limited than those of the prior art, the present invention has several advantages over the prior art.
Accordingly, the objects and advantages of the present invention are:
(a) to provide a lock nut that is simple in design and, therefore, easy and inexpensive to manufacture;
(b) to provide a lock nut that is rugged in structure and can be quickly mounted on the receiving bolt.
(c) to provide a lock nut that does not require any special tools to install or remove;
(d) to provide a lock nut that can be gripped with any of an assortment of standard tools but cannot be removed without unlocking it;
(e) to provide a lock nut that is not rendered ineffective by attempts to jam or break the lock mechanism such as by the use of a hammer or the like;
(f) to provide a lock nut that is designed with an understanding of the specific geometry of the intended use, and which relies on that geometry to provide an obstruction that interferes with the ability to remove the lock nut when in the locked position;
(g) to provide a lock nut that does not require the modification of the corresponding bolt in order to function;
(h) to provide a lock nut that can be threaded onto the receiving bolt in one configuration and, thereafter, can be locked in place in an alternate configuration.
A preferred embodiment of the lock nut was developed for the specific application of locking a nut on the hinge bolt of a Jeep Wrangler door. As it happens, just as is the case with many automobile wheels, Jeep Wrangler doors are often stolen. In their normal factory configuration, the doors can be stolen by removing just one nut from the door upper hinge bolt. The doors are in high demand as replacement parts. As evidence of the utility of this embodiment, there exists a commercial locking product to prevent theft of the Jeep Wrangler door. The product, manufactured by Tuffy Corporation of Cortez, Colo., was not listed herein as an example of prior art, because it does not rely on a locking nut mechanism. The Tuffy design relies on a cam which rotates over the hinge bolt, preventing the ability to lift the door off of the hinge.
The geometry of the Wrangler door hinge satisfies the two constraints of this invention in that the hinge bolt cannot be rotated and the geometry surrounding the bolt provides an obstruction that prevents the removal of the nut when in the locked configuration. In the case of this embodiment of the invention, the vehicle body itself acts as the obstruction. This embodiment includes a slotted nut that can be threaded onto the hinge bolt threads in place of the standard nut that comes with the Wrangler. Once the slotted nut has been threaded, a lock cylinder is locked in place on the slotted nut. The joined configuration of the slotted nut, locked together with the lock cylinder, is of such size that the lock nut interferes with the vehicle body if one tries to rotate the nut. The interference prevents the nut from being turned by more than 180 degrees, thereby preventing removal of the lock nut and securing the door against theft.
The preferred embodiment of the lock nut includes a slotted nut for threading on the end of the hinge bolt. The slotted nut includes a pin slot therethrough. A pin is dimensioned for receipt through the pin slot. The pin includes a plurality of sawtooth teeth and a pin stop. A lock cylinder pin slot, in a lock cylinder, receives a portion of the pin therethrough. The lock cylinder also includes a lock face with a key slot. When a lock key is inserted into the key slot and turned, internal workings of the lock cylinder engage the pin for securing the lock cylinder next to a side of the slotted nut.
An alternate embodiment is presented to illustrate the fact that this invention need not be comprised of multiple pieces. The aforementioned preferred embodiment used three separate piecesxe2x80x94a pin, a slotted nut, and a lock cylinder. The alternate embodiment uses a single piece which is hinged and can be locked either in a straight line or xe2x80x9cLxe2x80x9d shaped configuration. This invention requires that a lock nut be threaded onto a bolt in one configuration and, thereafter, be locked in place in a different configuration. The configuration change can be the result of adding pieces or of changing the shape of a single piece. This alternate embodiment could be used in the same application as the preferred embodiment. It could also be used to lock the wheels on many 4 wheel drive vehicles. Since on most 4 wheel drive vehicles the axle end extends beyond the plane formed by the base of the wheel lugs, this lock nut could be threaded on a wheel lug in the straight line configuration, then locked in the xe2x80x9cLxe2x80x9d shaped configuration. Once locked, the nut would be blocked by the axle if one were to attempt to rotate and remove it.
These and other objects of the present invention will become apparent to those familiar with the different types of lock nuts when reviewing the following detailed description, showing novel construction, combination, and elements as herein described, and more particularly defined by the claims, it being understood that changes in the embodiments to the herein disclosed invention are meant to be included as coming within the scope of the claims, except insofar as they may be precluded by the prior art.